Transmission shaft parts are one of the important parts of mechanical transmission on diesel locomotive. The function of the transmission shaft of Dongfeng 4 locomotive is to transmit the output power of the diesel engine to the hydrostatic gearbox, drive the two hydrostatic pumps to work and pump out the high-pressure hydrostatic oil. At the same time, according to the requirements of oil and water temperature, drive and adjust the hydrostatic motor to work and cool the high and low-temperature cooling water.
It can be seen that the transmission shaft mainly bears torque. On the one hand, the torque changes with the change of diesel engine speed, on the other hand, it increases with the increase of diesel engine output power. Therefore, the transmission shaft is subjected to alternating torque. After long-term use, cracks must begin to occur in the weak parts. If it cannot be found in time, there will be stress concentration at the crack, and the transmission shaft tear fault will occur in a short time.
The base materials of hollow shaft and spline shaft in transmission shaft are 40# steel and 45# steel. 45# steel belongs to medium carbon steel. The weldability of carbon steel will change obviously with the increase of carbon content. The higher the carbon content and the greater the thickness of the workpiece, the low plastic hardening structure will be produced in the near seam area under the action of welding thermal cycle. This brittle state plus large shrinkage stress will lead to cold cracks in the near seam area [1]. According to the carbon equivalent formula of international welding society, the carbon equivalent CEQ of 45# steel is calculated to be 0.67. Generally speaking, when its value is greater than 0.60, it has quite high crack sensitivity. In order to avoid cracks, strict welding process measures must be adopted.  
                                      Contributed by Xuchang Shenbang Machinery Manufacturing Co., Ltd